I am not an expert or have access to originals but this website seems to suggest your translation is wrong because your translation has 'of his Son' but it is not there in the Greek.
Without more information I would suggest your translation is incorrect and possibly adding eisegesis in order to avoid the plain meaning: that God made the church with His own blood.
Greek
Keep watch over
????????? (Prosechete)
Verb - Present Imperative Active - 2nd Person Plural
Strong's 4337: From pros and echo; to hold the mind towards, i.e. Pay attention to, be cautious about, apply oneself to, adhere to.
yourselves
??????? (heautois)
Reflexive Pronoun - Dative Masculine 3rd Person Plural
Strong's 1438: Himself, herself, itself.
and
??? (kai)
Conjunction
Strong's 2532: And, even, also, namely.
the
?? (t?)
Article - Dative Neuter Singular
Strong's 3588: The, the definite article. Including the feminine he, and the neuter to in all their inflections; the definite article; the.
entire
????? (panti)
Adjective - Dative Neuter Singular
Strong's 3956: All, the whole, every kind of. Including all the forms of declension; apparently a primary word; all, any, every, the whole.
flock
??????? (poimni?)
Noun - Dative Neuter Singular
Strong's 4168: A little flock. Neuter of a presumed derivative of poimne; a flock, i.e. group.
of
?? (en)
Preposition
Strong's 1722: In, on, among. A primary preposition denoting position, and instrumentality, i.e. A relation of rest; 'in, ' at, on, by, etc.
which
? (h?)
Personal / Relative Pronoun - Dative Neuter Singular
Strong's 3739: Who, which, what, that.
the
?? (to)
Article - Nominative Neuter Singular
Strong's 3588: The, the definite article. Including the feminine he, and the neuter to in all their inflections; the definite article; the.
Holy
????? (Hagion)
Adjective - Nominative Neuter Singular
Strong's 40: Set apart by (or for) God, holy, sacred. From hagos; sacred.
Spirit
?????? (Pneuma)
Noun - Nominative Neuter Singular
Strong's 4151: Wind, breath, spirit.
has made
????? (etheto)
Verb - Aorist Indicative Middle - 3rd Person Singular
Strong's 5087: To put, place, lay, set, fix, establish. A prolonged form of a primary theo to place.
you
???? (hymas)
Personal / Possessive Pronoun - Accusative 2nd Person Plural
Strong's 4771: You. The person pronoun of the second person singular; thou.
overseers.
?????????? (episkopous)
Noun - Accusative Masculine Plural
Strong's 1985: From epi and skopos; a superintendent, i.e. Christian officer in genitive case charge of a church.
Be shepherds
?????????? (poimainein)
Verb - Present Infinitive Active
Strong's 4165: To shepherd, tend, herd; hence: I rule, govern. From poimen; to tend as a shepherd of.
of the
??? (t?n)
Article - Accusative Feminine Singular
Strong's 3588: The, the definite article. Including the feminine he, and the neuter to in all their inflections; the definite article; the.
church
????????? (ekkl?sian)
Noun - Accusative Feminine Singular
Strong's 1577: From a compound of ek and a derivative of kaleo; a calling out, i.e. a popular meeting, especially a religious congregation.
of God,
???? (Theou)
Noun - Genitive Masculine Singular
Strong's 2316: A deity, especially the supreme Divinity; figuratively, a magistrate; by Hebraism, very.
which
?? (h?n)
Personal / Relative Pronoun - Accusative Feminine Singular
Strong's 3739: Who, which, what, that.
He purchased
????????????? (periepoi?sato)
Verb - Aorist Indicative Middle - 3rd Person Singular
Strong's 4046: To acquire, earn, purchase, make my own, preserve alive.
with
??? (dia)
Preposition
Strong's 1223: A primary preposition denoting the channel of an act; through.
[His]
??? (tou)
Article - Genitive Neuter Singular
Strong's 3588: The, the definite article. Including the feminine he, and the neuter to in all their inflections; the definite article; the.
own
????? (idiou)
Adjective - Genitive Neuter Singular
Strong's 2398: Pertaining to self, i.e. One's own; by implication, private or separate.
blood.
??????? (haimatos)
Noun - Genitive Neuter Singular
Strong's 129: Blood, literally, figuratively or specially; by implication, bloodshed, also kindred.